Process for the production of ( ) dihydrothebainone



United States Patent 3,438,989 PROCESS FOR THE PRODUCTION OF (:t) DIHYDROTHEBAINONE John Shave], Jr., Menham, and Glenn C. Morrison, Dover,

N .J assignors to Warner Lambert Pharmaceutical Company, Morris Plains, N.J., a corporation of Delaware No Drawing. Filed Mar. 10, 1967, Ser. No. 622,108

Int. Cl. C07d 43/32 U.S. Cl. 260-285 2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a new process for the production of (i) dihydrothebainone an intermediate in the total synthesis of morphine, which is a well-known drug useful as a narcotic analgesic.

Dihydrothebainone may be converted to morphine according to the processes described by Gates et a1. JACS 74 1109(1952), and Elad & Ginsburg J.C.S., 1954, 3052.

The process of this invention is carried out by reacting 3,4-dimethoxypheny1acetic acid and with m-methoxyphenethylamine at an elevated temperature such as 150- 200 C. to give an amide of the formula:

CHsO

On cyclodehydration of the amide (1) using a catalyst such as phosphorous oxychloride there is formed a dehydro intermedite which on reduction with an alkali metal borohydride such as sodium borohydride aifords a tetrahydroisoquinoline of the formula:

OCHa

onto EN Compound (2) may be converted to the corresponding N-lower alkyl derivative (3) by treatment with a lower alkyl ester such as ethyl formate and subsequent reduction with lithium aluminum hydride. Compound 3 has the following formula:

OCH

CHaO

3,438,989 Patented Apr. 15, 1969 wherein R is lower alkyl. Compounds (2) and (3) can be converted to the corresponding monohydroxy compounds 4 and 5, respectively, by treatment with an alkali metal such as sodium and an aliphatic alcohol such as tbutanol in liquid ammonia.

OCH:

CHSO RN 4) R=H (5) R=lower alkyl Further treatment of compounds 4 or 5 with the same reagents, while maintaining a higher alkali metal concentration, brings about reduction to the hexahydroisoquinoline 6 and 7.

01130 RN 6) R=H (7) R=lower alkyl Treatment of the enol ether 6 with a mineral acid such as 1N hydrochloric acid at a temperature of about to C. for about 10 to 20 minutes leads to the ketone 8.

Heating with acid over a period of about 1 to 3 hours results in the conjugated ketone 9.

no onto U The final result of exposure of 6 and 7 to acid in concentrated acid, for example 10 to 40% hydrochloric acid, for about 20 hours is the two cyclized ketones 10 and 12.

Prolonged acid treatment of the enol ether 7 leads to i) dihydrothebainone (11) and 2-hydroxy-3-methoxy- N-methy1morphin-6-one 13 NR HO NR CHaO CHaO (10) RzH (12) R:H (11) R=lower alkyl (13) Rzlower alkyl EXAMPLE 1 OCH;

CH3O

EXAMPLE 2 c1130 EN 1,2,3,4 tetrahydro 6 methoxy l veratrylisoquinoline.A solution of 82.2 g. of N (m-methoxyphenethyl)- 3,4dimethoxyphenylacetamide and 82 ml. of phosphorus oxychloride in 800 ml. of benzene was refluxed for 90 min. On pouring the reaction mixture into 1 l. of ether there was deposited 123 g. of a solid. The solid was dissolved in 1.5 l. of warm water (60), the pH adjusted to approximately 3 with 10% sodium hydroxide solution, and g. of sodium borohydride added over a min. interval. After the addition had been completed stirring was continued for an additional 20 min. The pH of the solution was adjusted to below 2 with 20% hydrochloric acid, after which it was made basic with 10% sodium hydroxide solution and extracted with ether. The ether layer was washed with water, dried over sodium sulfate, and the solvent removed. The residue (75 g.) after recrystallization from benzene-petroleum ether (B.P. 60) gave 60 g. (78%), M.P. 89.5-91. Further recrystallization from petroleum ether gave an analytical sample, M.P. 92-93.

Analysis.Calcd. for C H NO C, 72.82; H, 7.40; N, 4.47. Found: C, 72.99; H, 7.52; N, 4.23.

EXAMPLE 3 onto omo N 1,2,3,4 tetrahydro 6 methoxy 2 methyl 1 veratrylisoquinoline.A solution of 18.0 g. of 1,2,3,4,-tetrahydro-6-methoxy-l-veratrylisoquinoline in 250 ml. of ethylformate was refluxed for 20 hr. and then the excess formate distilled off. A solution of the residue in 550 ml. of tetrahydrofuran was added dropwise to a slurry of 10 g. of lithium aluminum hydride in 200 ml. of tetrahydrofuran. The mixture was stirred at room temperature for 4 hr. and then the excess hydride destroyed by the dropwise addition of water and sodium hydroxide solution. The tetrahydrofuran layer was decanted, dried over sodium sulfate, and the solvent removed. The residue, after recrystallization from petroleum ether (RP. 30- 60 gave 15.5 g. (74%) of a crystalline solid, M.P. 6971. Further recrystallization gave an analytical sample, M.P. 71-72.

Analysis.Calcd. for C H NO C, 73.36; H, 7.70; N, 4.28. Found: C, 73.34; H, 7.72; N, 4.55.

EXAMPLE 4 OCH3 q OHQO EV 1,2,3,4 tetrahydro 1 (3 hydroxy 4 methoxybenzyl)-6-methoxyisoquinoline.-To a solution of 10.9 g. of 1,2,3,4-tetrahydro-6-methoxy-l-veratrylisoquinoline in 500 ml. of tetrahydrofuran was added 600 ml. of ammonia. Over a 3 hour interval 8.3 g. of sodium and 27 ml. of t-butanol was added in ten equal portions. The ammonia was allowed to evaporate, one 1. of water was added, and the pH was adjusted to 8. On standing, there was deposited 7.3 g. (70%) of crystalline solid, M.P. 197-198". Recrystallization from chloroform gave an analytical sample, M.P. 196-197.

An alysis.Calcd. for C H NO C, 72.21; H, 7.07; N, 4.68. Found: C, 72.34; H, 7.31; N, 47.1.

EXAMPLE 5 OCH HN l

1,2,3,4,5,8 hexahydro -1 (3 hydroxy 4 methoxybenzyl)-6-methoxy-isoquinoline.To a solution of 9.4 g. of 1,2,3,4 tetrahydro l (3 hydroxy 4 methoxybenzyl)-6-methoxyisoquinoline in 500 ml. of tetrahydrofuran was added 350 ml. of ammonia. Then 1.0 g. of sodium was added and stirring continued for 0.5 hr. Over the next 2 hour interval 4.6 g. of sodium and 14 ml. of t-butanol were added alternately in ten equal portions. The remaining sodium was destroyed with isopropanol. The ammonia was allowed to evaporate, 1.3 l. of water was added, the pH adjusted to 8.5 with acetic acid, and the solution was extracted with methylene chloride. On concentration of the methylene chloride solution there was deposited 8.0 g. (84%) of a crystalline solid, M.P. 181. Recrystallization from chloroform gave an analytical sample, M.P. 177-1785".

Analysis.Calcd. for C H NO C, 71.73; H, 7.69; N, 4.65. Found: C, 71.56; H, 7.74; N, 4.58.

EXAMPLE 6 -oon,

HO CHsO 1,2,3,4-tetrahydro 1 (3-hydroxy-4-methoxybenzyl)- 6-methoxy-2-methylisoquinoline.-To a solution of 12.0 g. of 1,2,3,4-tetrahydro-6-methoxy-6-methyl l veratrylisoquinoline in 500 ml. of tetrahydrofuran was added 700 ml. of ammonia. Over a 6 hour interval 8.5 g. of sodium and 28 ml. of t-butanol were added in ten equal portions. The ammonia was allowed to evaporate, 1.5 l. of

water was added, the pH was adjusted to 8 with acetic acid, and the solution was extracted with methylene chloride. The methylene chloride layer was Washed with water, dried over sodium sulfate, and the solvent was removed. The residue, after recrystallization from isopropyl ether, aiforded 6.8 g. (59%) of a solid, M.P. 105-106". Further recrystallization gave an analytical sample, M.P. 109.5-1

Analysis.Calcd. for C H NO C, 72.82; H, 7.40; N, 4.47. Found: C, 73.22; H, 7.46; N, 4.70.

EXAMPLE 7 OCH:

CHSO N 1,2,3,4,5,8 hexahydro-1-(3-l1ydroxy-4-methoxybenzyl)- 6-methoxy-2-methylisoquinoline.-To a solution of 6.0 g. of 1,2,3,4 tetrahydro-1-(3-hydroxy-4-methoxybenzyl)-6- methoxy-Z-methylisoquinoline in 350 ml. of tetrahydrofuran was added 300 ml. of ammonia. Then 1.0 g. of sodium was added and stirring was continued for 0.5 hours. Over the next 3 hour interval 4.35 g. of sodium and 33 ml. of t-butanol were added in ten equal portions. The excess sodium was destroyed with ammonium chloride. The ammonia was allowed to evaporate, 1.5 l. of water added, the pH was adjusted to 8.5 with acetic acid, and the solution was extracted with ether. The ether solution was washed with water, dried over sodium sulfate and the solvent was removed. Crystallization of the residue from isopropyl ether-Skelly solve B afforded 4.1 g. (68%) of a solid, M.P. 1155-1165". Recrystallization from isopropyl ether gave an analytical sample, M.P. 116.5117.5.

Analysis.-Calcd. for C H NO C, 72.35; H, 7.99; N, 4.44. Found: C, 72.63; H, 8.18; N, 4.38.

EXAMPLE 8 EXAMPLE 9 CHQO 1,2,3,4,8,8a-hexahydro 1 (3-hydroxy-4-methoxyben- Zyl)-6(7H)-isoquinoline.A solution of 0.50 g. of 1,2,3, 4,5,8-hexahydro-1-(3 hydroxy-4-methoxybenzyl)-6-methoxyisoquinoline in 6 ml. of 1 N hydrochloric acid was heated on the steam bath for 1 hr. The reaction mixture Was neutralized with saturated sodium bicarbonate solution and extracted with chloroform. Removal of the solvent atforded, after recrystallization from ethyl acetate, 0.20 g. (36%) of a solid, M.P. 186-188. Recrystallization from acetonitrile gave an analytical sample, M.P. 191.5192.

Analysis.-Calcd. for C H NO C, 71.05; H, 7.37; N, 4.87. Found: C, 71.20; H, 7.60; N. 4.76.

EXAMPLE 10 OCH;

HO I omo- U CHaO I! ll 0 O Cyclization of 1,2,3,4,5,8-hexahydro-1-(3-hydroxy-4- methoxybenzyl)-6-methoxyisoquinoline.-A solution of 8.0 g. of 1,2,3,4,5,8-hexahydro-1-(3-hydroxy-4-methoxybenzyl)-6-methoxyisoquinoline in ml. of hydrochloric acid was refluxed for 20 hours. The pH of the reaction mixture was adjusted to 8.5 with ammonium hydroxide, and the solution was extracted with chloroform. The chloroform layer was washed with 25% sodium hydroxide solution, and water, dried over sodium sulfate, and the solvent was removed. The residue was dissolved in benzene and Skellysolve B was added. A solid was deposited, which after recrystallization from acetone- Skellysolve B, afforded 40 mg. (1%) of (1L) des-N-methyldihydrothebainone, M.P. 164164.5.

Analysis.Calcd. for C H NO C, 71.05; H, 7.37; N, 4.87. Found: C. 70.95; H, 7.36; N, 5.01.

The sodium hydroxide layer was neutralized to pH 8 with acetic acid, and extracted with chloroform. The chloroform solution was dried over sodium sulfate and the solvent was removed. Crystallization of the residue from isopropanol afforded 114 mg. (2%) of 2-hydroxy- 3-methoxymorphin-6-one, M.P. 225228. Further recrystallization gave an analytical sample, M.P. 230.5- 231.5.

Analysis.--Calcd. for C H NO C, 71.05; H, 7.37; N, 4.87. Found: C, 71.13; H, 7.48; N, 4.68.

EXAMPLE 1 1 N-CHs H 0 N-CH3 CH3O CHaO Cyclization of l,2,3,4,5,8-hexahydro-1-(3-hydroxy-4- methoxybenzyl) 6 methoxy-2-methylisoquinoline.-A solution of 6.3 g. of 1,2,3,4,5,8-hexahydro-l-(3-hydroxy- 4-methoxybenzyl)-6-methoxy2 methylisoquinoline in 250 ml. of 10% hydrochloric acid for 20 hours. The pH of the reaction mixture was adjusted to 8.5 with 40% sodium hydroxide solution and the solution was extracted With methylene chloride. The methylene chloride layer was washed with water, dried over sodium sulfate, and the solvent was removed. Crystallization of the residue from isopropyl ether afforded 2.2 g. (37%) of 2-hydroxy- 3-methoxy-N-methylmorphine-6-one, M.P. 194197.5. Recrystallization from isopropanol gave an analytical sample M.P. 200201.

Analysis.Calcd. for C H NO C, 71.73; H, 7.69; N, 4.65. Found: C, 71.43; H, 7.73; N, 4.76.

The filtrate from the crystallization was concentrated to dryness and the residue was chromatographed on 80 g. of alumina. Elution with 1% methanol in ether gave, after recrystallization from isopropyl ether 0.19 g. (3%) of (i) dihydrothebainone, M.P. 177.5178.

Analysis.-Calcd. for C H NO C, 71.73; H, 7.69; N, 4.65. Found: C, 71.74; H, 7.75; N, 4.81.

It is understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to Secure by Letters Patent is:

1. A process which comprises:

(a) Contacting a compound of the formula:

CHsO- CHaO RN wherein R is hydrogen or lower alkyl with an alkali metal and an aliphatic alcohol in liquid ammonia to obtain a compound of the formula:

(b) Contacting compound 2 in a higher concentration of the alkali metal and an aliphatic alcohol in liquid ammonia to obtain a compound of the formula:

c1130 RN 8 (c) Contacting compound 3 with a mineral acid at a temperature of about to 95 for 10 to 15 minutes to yield a ketone of the formula:

((1) Contacting compound 4 with a mineral acid at a temperature of about 80 to 95 for about 60 minutes to yield a compound of the formula:

onto RN wherein R is hydrogen or lower alkyl at a temperature of about 80 to C. for at least 20 hours in the presence of a strong non-oxidizing mineral acid.

References Cited UNITED STATES PATENTS 2,797,221 6/1957 Gates 260285 3,314,964 4/ 1968 Shavel et a1. 260-288 3,395,152 7/1968 Shavel et al. 260-288 ALEX MAZEL, Primary Examiner.

D. G. DANS, Assistant Examiner.

U.S. Cl. X.R. 

